Lighting systems for areal illumination typically comprise (1) a set of “luminaires” (light fixtures comprising mounting hardware and one or more light-emitting elements such as incandescent or fluorescent bulbs or arrays of light-emitting diodes [LEDs]), together with (2) one or more sensor elements (motion sensors, light sensors, and the like), (3) control devices (such as dimmers and switches), and (4) power drivers to set the output light level of each luminaire as a function of sensor outputs and control device settings. Such systems can range in complexity from a single wall switch and bulb to commercial building lighting systems comprising hundreds of luminaires, sensors, and control devices.
A common way to specify, configure, and install such systems requires the use of discrete components, where each of the above elements are purchased separately, and the control logic is implemented by the way the components are connected together using wired or wireless connections. Where convenient, certain elements can be physically grouped. For example, an outdoor security light fixture can have a motion sensor built into the fixture, or a table lamp can have an on/off switch built in. Often, however, such combinations are not used, and each element is separately purchased, installed, and wired together in order to create functional groups.
As the total number of components increases, there can be a need for more sophisticated control systems. These are typically implemented using electronic control systems, which can be implemented using either custom electronics or software running on a more general-purpose control device such as a digital computer. Such systems require a trained engineer to manually connect all devices, describe the system to the control hardware and software, and to define the control functions to be implemented.
A number of standards have been developed for such control systems. A commonly used standard is the Digital Addressable Light Interface (DALI) which is described in Appendix E of IEC60929, a standard for fluorescent lamp ballast control managed by the International Electrotechnical Commission. DALI uses bidirectional data exchange with each luminaire, and a DALI controller can query and set the status of each luminaire. As an example of the kind of control functionality that can be implemented using DALI, an engineer can define groups that associate a set of luminaires with a set of one or more motion sensors, dimmers, and/or switches, all of which have been connected to the control system. While installations complying with the DALI standard are significantly more flexible and easier to reconfigure than a completely hard-wired installation, the process of commissioning a complete lighting system still requires a skilled engineer to define the groups in accordance with the physical installation and further to define the control logic to be implemented.
The cost of discrete components as well as the cost of installation and programming labor have thus far inhibited wide-spread adoption of sophisticated control systems. There are, nevertheless, obvious cost savings and performance benefits that can be realized by intelligently managing the on-time and on-intensity of each light source within lighting systems. Potential saving in electricity usage can be large, and safety and security can be enhanced. Nevertheless, to be widely adopted, the components need to be inexpensive, and the installation should be quick and easy and all configuration work should be possible within the skill range of an average commercial electrician or that of building maintenance personnel.
In order to reduce installation and commissioning costs as well as the skill level required to implement these tasks, it is possible to automate some of the commissioning steps. For example, U.S. Patent Application 2009/0045971 A1 describes estimating the distance between pairs of luminaires using either received signal strength or time-of-flight of a radio-frequency communication signal used to communicate between luminaires.